a. Field of the Invention
This disclosure relates to a system and method for presenting information representative of lesion formation in tissue during an ablation procedure. More particularly, this disclosure relates to a system and method for automatically characterizing lesion markers and placing the lesion markers onto an image or model of tissue so as to form a lesion formation map.
b. Background Art
It is known that ablation therapy may be used to treat various conditions afflicting the human anatomy. One such condition that ablation therapy finds particular applicability is in the treatment of atrial arrhythmias, for example. When tissue is ablated, or at least subjected to ablative energy generated by an ablation generator and delivered by an ablation catheter, lesions form in the tissue. More particularly, an electrode or electrodes mounted on or in the ablation catheter are used to create tissue necrosis in cardiac tissue to correct conditions such as atrial arrhythmia (including, but not limited to, ectopic atrial tachycardia, atrial fibrillation, and atrial flutter). Atrial arrhythmias can create a variety of dangerous conditions including irregular heart rates, loss of synchronous atrioventricular contractions and stasis of blood flow which can lead to a variety of ailments and even death. It is believed that the primary cause of atrial arrhythmia is stray electrical signals within the left or right atrium of the heart. The ablation catheter imparts ablative energy (e.g., radio frequency energy, cryoablation, lasers, chemicals, high-intensity focused ultrasound, etc.) to cardiac tissue to create a lesion in the cardiac tissue. The lesion disrupts undesirable electrical pathways and thereby limits or prevents stray electrical signals that lead to arrhythmias.
One challenge with ablation procedures is in the assessment of the integrity or efficacy of the lesion formed during the ablation procedure. Conventional techniques are both empirical and subjective. More particularly, conventional techniques include the clinician or another user of the system monitoring ablation description characteristics and parameters thereof, interpreting those characteristics/parameters, and manually causing markers to be placed onto an image of the tissue being ablated to represent the monitored characteristics.
Conventional techniques such as these suffer from a number of drawbacks, however. For example, oftentimes ablation description parameters that the clinician monitors are displayed on display monitors of different devices, thereby rendering the monitoring difficult and the interpretation prone to error. Further, many parameters are contaminated with RF, cardiac motion, or respiratory motion artifacts, thereby contaminating the signals, which can lead to errors in both lesion marker location and lesion quality estimation. Additionally, respiratory artifacts and ablation generator (RF) impedance can lead to unreliable measurements, such as, for example, impedance drop measurements. Further, visualization of lesion quality is complicated because clinicians indirectly control lesion marker placement and visualization.
Existing software tools cannot automatically quantify and visualize lesion integrity. In certain existing systems, clinicians manipulate catheters within a sterile field, while a separate operator places lesion markers on a mapping system in a non-sterile field. Therefore, operators, and not catheter manipulating clinicians, are manually placing lesion markers on an image of the tissue being ablated. Once the lesion marker is placed, there is no way to determine whether the operator understood or correctly implemented the clinician's lesion efficacy criteria. Thus, there is no way to determine whether the location and/or the coloration, for example, of the manually-placed lesion markers reflect the clinician's lesion efficacy criteria. As a result, errors in the location of lesion markers can mislead the clinician into erroneously believing that certain areas have been ablated or not ablated. Errors in the coloration and size of the markers can mislead the clinician into erroneously believing that the lesion integrity or efficacy is poor when it is in fact good, or good when it is in fact poor.
Accordingly, the inventors herein have recognized a need for a system and method for characterizing and placing lesion markers on an image of tissue being subjected to an ablation procedure that will minimize and/or eliminate one or more of the deficiencies in conventional systems.